efficiency

• What is the main topic discussed in the video?

  The efficiency of energy transfer in devices
• Why is energy not always transferred into the intended form?


  Because most devices aren't 100% efficient
• What is efficiency in the context of energy transfer?


  • Proportion of input energy converted to useful output
  • Useful energy output is considered useful energy
  • Waste energy is non-useful energy output
• What is the equation to calculate efficiency in terms of energy?


  Efficiency = useful energy output / total energy input
• What is the equation to calculate efficiency in terms of power?


  Efficiency = useful power output / total power input
• If a lamp has an input energy of 300 joules and outputs 45 joules as light energy, what is its efficiency?


  0.15
• If a lamp has an input energy of 300 joules and outputs 225 joules as light energy, what is its efficiency?


  0.75
• How do you convert efficiency figures from decimal to percentage?


  By multiplying by 100
• If the efficiency of the incandescent bulb is 0.15, what is its efficiency in percentage terms?


  15%
• What happens if you calculate efficiency incorrectly and get a value greater than 1?


  It implies more energy output than input, which is impossible
• What principle explains why energy cannot be created or destroyed?


  The conservation of energy principle
• If a microwave has an efficiency of 70% and a total power input of 800 watts, what is the useful power output?


  560 watts
• How do you convert the efficiency percentage of 70% into a decimal?


  By dividing by 100 to get 0.7
• What is the relationship between waste energy and useful output in devices designed to produce heat?


  • Devices like electric heaters produce thermal energy
  • Thermal energy is considered useful output in this context
  • Waste energy is not always non-useful in heat-producing devices
• What is the maximum efficiency of any device?


  No device is 100% efficient
• What type of energy do most devices produce as waste energy?

  Thermal energy